It is proposed in West German Patent Application No. P 3218863.3 that a continuous-flow water heater be in the form of a vertical cylindrical tank containing a concentric array of electrical heating elements, and, that heated water be withdrawn from an upper end of the tank. In order to increase the rate of heat exchange between the heaters and the water to be heated, the water is caused to move within the tank in a cyclic path by introducing the water tangentially into the tank at positions spaced vertically of the tank. By so doing, the formation of steam bubbles in the tank is reduced, as is the mechanical noise produced by such steam bubbles.